Quadriceps Muscle Layer Thickness and its association with frailty in critically ill patients: A prospective observational study

Background: Frailty is a well-recognized clinical entity known to influence the outcomes of critically ill patients. Muscle ultrasound, particularly Quadriceps Muscle Layer Thickness (QMLT), assesses muscle mass, which is a key component determining frailty. However, no studies have assessed the association between frailty and QMLT. This study aimed to determine the association between the QMLT and frailty in critically ill elderly patients.

Method: In this prospective, observational, single-center study conducted in an ICU in India, patients aged >65 years were enrolled. Baseline frailty was assessed using the Clinical Frailty Scale (CFS). Quadriceps muscle thickness was measured via axial cross-section ultrasound at admission. Patients were categorized as non-frail (CFS 1-4) and frail (CFS ≥5), and their characteristics were compared. Multivariate regression analysis was used to identify factors associated with frailty.

Results: 120 patients were included. The median APACHE II and SOFA scores were 19 [IQR 14.25-23] and 4.5 [IQR 3-6], respectively. The median age was 75 years [IQR 70-82]; 62.5 % were male. The most common comorbidities were diabetes mellitus (60 %) and hypertension (59 %). 65 % were mechanically ventilated. 65 % of patients were frail. Frail patients had higher mortality (37.17 % vs. 16.66 %, p = 0.022). QMLT was lesser in frail than non-frail (1.77 cm vs 2.21 cm, p < 0.001). QMLT decreased with an increase in CFS (p < 0.001). Frail and non-frail patients were further divided into four groups based on the median QMLT (1.96 cm). Frail patients with QMLT below the median had a higher 28-day mortality than non-frail and frail patients with QMLT above the median (48.97 % vs. 16.12 % vs. 18.18 % vs. 17.24 %, p = 0.003). Frailty was independently associated with increasing age (OR, 1.14; 95 % CI: 1.055-1.231, p = 0.001), higher APACHE II score (OR, 1.078; 95 % CI: 1.009-1.151, p = 0.025), and lower QMLT (OR, 0.205; 95 % CI: 0.083-0.509, p = 0.001).

Conclusions: We found an independent association between Quadriceps Muscle Layer Thickness (QMLT) and frailty. QMLT decreased progressively with CFS scores. Frail patients with lower QMLT had increased 28-day mortality. These findings highlight the role of incorporating QMLT measurements along with CFS in frailty evaluations to improve decision-making in critically ill elderly patients.